Golf car having disk brakes and single point latching brake

ABSTRACT

A golf car having a hydraulic fluid brake system. The hydraulic fluid brake system is implemented as a disk brake system which is responsive to hydraulic fluid pressure generated from a master cylinder. A brake pedal and associated linkage provides input to a master cylinder to generate a hydraulic fluid pressure to control a brake caliper assembly. The brake pedal has a range of travel, where a first portion of the range defines a service mode of operation and a second portion of the range defines a parking mode of operation. In the parking mode of operation, the brake pedal and linkage engages a detent to maintain application of the brake to provide a parking mode of operation. An accumulator in the brake system provides an input force to maintain hydraulic fluid pressure sufficient to retain a parking mode of operation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/517,302, filed Mar. 2, 2000, now U.S. Pat. No. 6,223,865, whichclaims the benefit of priority of U.S. Provisional Application Ser. No.60/122,405, filed Mar. 2, 1999, the entire contents of which are herebyexpressly incorporated by reference into the present application.

BACKGROUND

1. Technical Description

The present invention relates generally to golf cars having disk brakesand, more particularly, to golf cars having hydraulically actuated diskbrakes, a single point latching mechanism, and an integrated acceleratorpedal and brake pedal release of the brake system when in a parkingmode.

2. Description of Related Art

Most golf cars, and other small utility vehicles, have brake systems inone form or another. Examples of such systems may be found withreference to U.S. Pat. Nos. 4,867,289, 5,158,415, and 5,713,189, thedisclosures of which are incorporated by reference herein for theirtechnical teachings. While the above referenced patent documents, andother references, discuss application of brakes to utility vehicles andgolf cars, brake systems for small vehicles and golf cars may yet beimproved to increase the ease of use, feel, performance, serviceability,and the like.

The typical golf car brake system includes a brake pedal andinterconnected accelerator pedal. When the brake pedal is depressed apredetermined distance, the brake system operates in a normal or servicemode. Depressing the brake pedal further engages a parking mode whichmaintains the golf car in a stationary position. When engaging theparking mode, most brake pedals have numerous mechanical detentpositions to enable progressive application of increasing braking force.In some golf cars, the first detent position does not apply sufficientbraking force to maintain the golf car in a stationary position.However, because each detent position often generates an audible click,an operator may assume that the parking brake has been sufficientlyengaged when the parking brake has yet to be sufficiently engaged.Further, conventional brake systems are mechanically sprung to returnthe brake pedal to a non-depressed position. When disengaging theparking brake, such brake systems often generate a particularly loud,audible pop which can be somewhat distracting to the operator.

It is therefor an object of the present invention to provide a brakesystem for a golf car which significantly improves upon the prior brakesystems.

Lightweight off-road utility vehicles used as personnel and cargocarriers, such as golf carts, are much smaller than conventionalautomobiles used on the highways. Their tires and wheels are muchsmaller, and the space beneath the vehicle body is much smaller, thusproviding much less room for the mounting of braking mechanisms at therear wheels. While the brakes used on golf cars have historically beenvery satisfactory for stopping purposes, the service interval betweenchanging of brake pads or shoes has been relatively short, and often isabout one year for a golf car that sees extensive use. As labor costsmount for golf course operators and the like, there is a growingperception that is would be desirable to have a brake system whose padsor shoes last longer than conventional brakes, thus reducing the overallcosts of providing periodic brake service to the vehicles and allowingthe vehicles to be in service for longer periods of time, before beingpulled out of service for a brake inspection and possible brakepad/brake shoe replacement. Further, when pulled out of service, thereis a continuing need to minimize downtime and to minimize the difficultyand amount of labor required to replace the brake shoes or pads.

Accordingly, another object of the present invention is to provide animproved braking mechanism that will have a long service life for use onthe rear wheel of small off-road utility vehicles such as golf cars thathave small wheels and wide tires. A related object is to provide a diskbrake caliper mechanism that is easy to service, and that requiresminimal disassembly to change the replaceable brake pads within thebrake caliper assembly. A further object is to provide an extremelycompact construction for a robust hydraulic disk brake assembly which isable to fit within the very confined space in the vicinity of the wheelhub and wheel rim of a small-size off-road vehicle such as a golf car. Arelated object is to provide a compact construction for a brake caliperassembly which features excellent parking braking power and a very longservice life between brake pad changes. Another object is to provide aneasily-assembled yet compact brake caliper assembly that is of very lowprofile, such that it can fit between a small-diameter wheel rim and thecentral cylindrical housing portion of a hub and rotor assembly on aconventional light-weight utility vehicle having a small diameter widewheel rim associated with wide-profile tires such as those found on agolf car.

SUMMARY OF THE INVENTION

The present invention is directed to a golf car including a framesupported on a plurality of wheels. A prime mover provides driving forceto selected wheels to displace the golf car. The golf car also includesan operator or passenger area supported by the frame and an integratedbrake pedal and accelerator pedal assembly. A hydraulically operatedbrake system receives input from the brake pedal and generates an outputto control a hydraulically operated braking device. The brake systemoperates in a normal mode by partially depressing the brake pedal, andthe brake system operates in a parking mode by depressing the brakepedal further. When the brake system is in the parking mode, the brakesystem may be released by depressing either the brake pedal oraccelerator pedal.

The present invention is also directed to a brake system for a golf carincluding an integrated brake pedal and accelerator pedal assembly. Ahydraulic brake actuation system receives input from the brake pedal andgenerates an output to control a hydraulically operated braking device.An accumulator stores braking energy when in a parking mode andmaintains a predetermined minimum hydraulic pressure throughout thebrake system. The brake system operates in a normal mode by partiallydepressing the brake pedal, and the brake system operates in a parkingmode by depressing the brake pedal further. When the brake system is inthe parking mode, the brake. system may be released by depressing one ofthe brake pedal or accelerator pedals.

The present invention is also directed to a golf car including a framesupported on a plurality of wheels. A prime mover provides drivingforce. to selected ones of the plurality of wheels to displace the golfcar. An integrated brake pedal and accelerator pedal assembly includes abrake pedal having a range of travel. A first portion of the range oftravel defines a service mode of operation, and a second portion of therange of travel defines a parking mode of operation. The integratedbrake pedal and accelerator pedal assembly includes a lock position forthe parking mode of operation and generates a single audible sound whendepressed to the lock position. A hydraulically operated brake systemreceives input from the brake pedal and generates an output to control ahydraulically operated braking device. When the brake system is in theparking mode, the brake system may be released by depressing one of thebrake pedal or accelerator pedal.

This invention is also directed to a golf car including a framesupported on a plurality of wheels. A prime mover provides driving forceto selected ones of the plurality of wheels to displace the golf car. Anintegrated brake pedal and accelerator pedal assembly. A hydraulicallyoperated brake system receives input from the brake pedal and generatesa hydraulic output signal. A brake rotor attaches to at least one of thewheels of the golf car. A first caliper assembly has brake padsdisplaceable in accordance with the hydraulic output signal. The brakepads contact the brake rotor to cause friction. The friction retardsmovement of the brake rotor and associated wheel. The brake systemoperates in a normal mode by partially depressing the brake pedal. Thebrake system operates in a -parking mode by depressing the brake pedalfurther. When the brake system operates in the parking mode, the brakesystem may be released by depressing one of the brake pedal oraccelerator pedals.

For a more complete understanding of the invention, its objects andadvantages, reference should be made to the following specification andto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings, which form an integral part of the specification, are tobe read in conjunction therewith, and like reference numerals areemployed to designate identical components in the various views:

FIG. 1 is an elevational, partial cut-away view of a golf car includinga brake system arranged in accordance with the principles of the presentinvention;

FIG. 2 is a block diagram of the brake system arranged in accordancewith the principles the present invention;

FIG. 3 is a perspective view of the golf car support frame andcomponents of the brake system;

FIG. 4 is an assembled view of the brake and accelerator pedal assembly;

FIG. 5 is an exploded view of the brake pedal and the accelerator pedalassembly;

FIG. 6 is a top view of the brake pedal and accelerator pedal assembly;

FIGS. 7 and 8 are a partial, vertical sectional views of the brake pedaland accelerator pedal assembly;

FIG. 9 is a graph depicting hydraulic pressure as a function of brakepedal displacement;

FIG. 10 is a block diagram of a brake system of the present inventionutilizing a drum brake system;

FIG. 11 is a block diagram of the brake system of the present inventionutilizing a brake band system;

FIG. 12 is an interior perspective view of a hub and caliper assembly;

FIG. 13 is an exterior perspective view of a hub and caliper assembly;

FIG. 14 is an exploded view of a caliper assembly of FIGS. 12 and 12;

FIG. 15 is an expanded perspective view of the caliper assembly;

FIG. 16 is a bottom view of the caliper assembly; and

FIG. 17 as an elevational view of the integral wheel, hub, and rotorassembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 depicts a golf car 10 having a brake system arranged inaccordance with the principles of the present invention. Golf car 10includes a pair of front wheels 12 and a pair of rear wheels 14. Rearwheels 12 preferably operate as steering wheels to control the directionof travel of golf car 10. Rear wheels 14 preferably function as drivewheels for propelling golf car 10.

Golf car 10 includes a seat 16 which preferably accommodates a driverand a passenger. Golf car 10 also includes a steering wheel 18 whichcontrols the direction of front wheels 12. An accelerator pedal 82 and abrake pedal 80 enable the operator to control acceleration and brakingof golf car 10. Accelerator pedal 82 and brake pedal 80 preferably aresuspended from support members which hang generally downwardly fromunderneath a front cowling 24, as will be described herein.

Still referring to FIG. 1, an entire brake actuator and release assembly50 is configured as a modular unit mounted above the floorboard 26 andat least partially beneath the front cowling 24. It therefore lacks anyuhderhanging components that extend beneath the floorboard 26. Thisconfiguration is advantageous for several reasons. For instance, thereis no risk that any components of the brake system 50 will be damaged byobstructions over which golf car 10 may travel. Moreover, the systemcomponents are isolated from corrosive substances over which the vehiclemay travel such as water, fertilizers, etc.

FIG. 2 depicts a particular feature of golf car 10, namely, brake system50. Accelerator pedal 82 controls operation of an electric motor 32which is powered by a source of electrical energy (not shown). Electricmotor 32 includes one or a pair of output shafts 34 which control driveto respective hubs 38. It should be noted that reference numerals in thedrawings may include an R or L suffix to designate a component ascorresponding to the left or driver's side or the right or passenger'sside of golf car 10. Respective hubs 38 drive rear wheels 14 to propelgolf car 10. While motor 32 is described herein as an electric motor,one skilled in the art will recognize that rear wheels 14 may bepropelled by a gasoline powered engine and transmission or othersuitable power source.

Brake system 50 will generally be described herein as a hydraulicallyactuated brake system wherein displacement of brake pedal 80 generates ahydraulic force to operate a braking element, such as a disk, drum, orband brake system, as will be described herein. Brake system 50 includesbrake pedal 80 which connects to and displaces a linkage 42. Linkage 42provides an input to a master cylinder 60. Master cylinder 60 operatesgenerally as a conventional master cylinder in which depressing brakepedal 80 provides an input to master cylinder 60 which generates anincrease in hydraulic fluid pressure output on hydraulic control line46.

Hydraulic control line 46 provides fluid pressure to caliper assemblies48. Each caliper assembly 48 includes opposing pads 44. A brake rotor 40moves rotationally in accordance with hubs 38. Pads 44 apply africtional force to brake rotor 40 to retard movement of brake disk 52,thereby applying a braking force upon wheels 14. Caliper assemblies 48thus operate generally as is known to one skilled in the art. In orderto maximize braking force, an optional second pair of caliper assemblies54 may be arranged to provide additional retarding force upon brakerotor 40. A particularly attractive feature of utilizing two caliperassemblies on a single brake disk is to compensate for space limitationsinherent with the generally small diameter of wheels 14 of a typicalgolf car 10.

As described above, depressing brake pedal 80 causes master cylinder 60to generate a hydraulic fluid output pressure on hydraulic control line46 which is applied to caliper assemblies 48 and to calipers assemblies54 if present. An increase in hydraulic fluid pressure causes brake pads44 to move toward brake rotor 40 to generate a frictional force whichretards movement of wheels 14.

Brake system 50 has two modes of operation. A first mode of operation, aservice mode, of brake system 50 reduces the speed of golf car 10 to alower speed, a stop, or to prevent unwanted acceleration of golf car 10when going down hill. A second mode of operation, a parking mode, ofbrake system 50 maintains golf car 10 in a stopped position until theparking mode has been released.

Brake pedal 80 has a range of travel for causing master cylinder 60 tooutput a hydraulic fluid pressure suitable for stopping golf car 10 ormaintaining golf car 10 in a stopped position. A first portion of therange of travel of pedal 80 effects a service mode of operation forreducing the speed of golf car 10 or to prevent unwanted acceleration ofgolf car 10 when going down hill. Depressing brake pedal 80 furtherplaces brake system 50 in a parking mode. Linkage 42 includes a detentsetting for engaging and holding brake pedal 80 in a predeterminedposition while in the parking mode. When in this parking mode, theaccumulator 62 provides a supplemental input to master cylinder 60 tocompensate for any hydraulic fluid pressure drop through seal leakageand the like. Accumulator 62 maintains hydraulic fluid pressure so thatcaliper assemblies 48 provide suitable parking brake force upon brakerotor 40 and associated wheels 14.

Brake pedal 80 and linkage 42 cooperate to include a single detent whichis engaged when brake pedal 80 travels a predetermined distance so as tocause master cylinder 60 to output a sufficient hydraulic fluid pressureto prevent displacement of wheels 14. When brake pedal 80 has engaged adetent position to define a parking mode of operation, brake system 50can be disengaged from the parking mode of operation by depressingeither brake pedal 80 or accelerator pedal 82. Accelerator pedal 82 ismechanically linked to brake pedal 80 to enable release of the brakesystem 50 from the parking mode of operation.

With particular reference to FIG. 3, golf car 10 includes a vehicleframe 56. Frame 56 provides a support to which brake and acceleratorpedal assembly 58 connects. Rear axle assembly 64 supports a rearportion of frame 56 via a suspension (not shown). As shown in FIG. 3,brake and accelerator pedal assembly 58 mounts to an upper portion 52 offrame 56 so that brake pedal 80 is suspended downwardly on lever arm 88and accelerator pedal 82 is suspended downwardly upon accelerator arm172.

Several features of brake system 50 will now be described. When theparking mode is engaged, brake system 30 generates a single audibleclick or pop sound. The sound indicates that the parking mode has beenproperly engaged by the operator. The benefit of a single audible soundis to provide a clear indication that the parking mode has been engaged.This feature improves upon conventional braking systems where multipleaudible sounds may be generated when engaging a parking mode. In suchsystems the operator could incorrectly assume that while the brake pedalis locked in a position that generates a sufficient braking force, aninsufficient parking brake force could be applied.

Brake system 50 inherently has less hysteresis associated with stictionthan brake systems utilizing mechanical components, particularlyhysteresis caused by cables running over contact points. Reducedhysteresis provides a brake system 50 which requires less force forselecting either the service or parking modes verses a mechanical systemwhich requires greater force to properly engage a service or parkingmode. Because hysteresis is inherently less in a hydraulic system andbecause hysteresis in mechanical systems typically increases over time,hydraulic brake system 50 significantly reduces hysteresis concernsproblem over the lifetime of golf car 10.

Hydraulic brake system 50 has a self-adjusting system which compensatesfor wear in brake pads 44. Self adjustment occurs because the systemallows extra fluid from the hydraulic reservoir of master cylinder 60 tobe added to the system. Using caliper design features well known in theart, the seals of the hydraulic cylinders in the brake calipers insure auniform return of brake pads 44 to equal distances away from brake disk52. These benefits may be further realized by utilizing a bladder-basedhydraulic reservoir which provides several additional advantages. Thebladder type hydraulic reservoir ensures minimal loss of hydraulic fluidthrough the top of the reservoir. This avoids introduction ofcontaminants such as water, dirt, and atmospheric transfer which mayoccur.

Hydraulic brake system 50 utilizes a synthetic fluid which isnon-hygroscopic. A non-hygroscopic fluid does not absorb any fluid.Conventional brake fluid, on the other hand, absorbs moisture directlythrough rubber hoses and seals and other places where conventional brakesystems are open to the atmosphere, including the reservoir. Thistransfer occurs even through seals which are frequently water vaporpermeable. Thus, while many seals resist moisture in a liquid form, manysuch seals do not resist moisture in the form of a gaseous vapor.Hygorscopic brake fluid also often accelerates internal breakdown ofmetal brake system parts, while non-hygroscopic, synthetic fluidsignificantly reduces internal breakdown of metal brake system parts.Non-hygroscopic fluids provide a non-polar property, which yields anenvironmentally friendly brake fluid. Most grass plants will not absorbthe non-hygroscopic, synthetic fluid, while typical conventional brakefluids may be absorbed by and damage plant life yet.

Conventional brake fluids, while possibly avoiding water absorption,also absorb air. The absorption of air into the brake fluid creates aspongy brake feeling and can also raise other issues such as cavitationand outgassing. Outgassing occurs when a vehicle remains exposed for alengthy period of time in a high altitude condition. Bringing the golfcar down to lower elevations and thus higher atmospheric pressure causesair entrained in the liquid at higher elevations to boil off at thelower elevations. This introduces variation into the hydraulic system.

Hydraulic brake system 10 also provides a positively-sealed, pressurizedhydraulic brake system. In a parking mode, hydraulic brake system 10generates at least 750 pounds per square inch (PSI). This pressurizationexceeds internal hydraulic fluid pressure typically utilized inconventional hydraulic braking systems, particularly at rest. Inconventional hydraulic braking systems, the parking mode is engagedthrough a mechanical-type emergency brake or transmission lock. Brakesystem 50 utilizes a hydraulic system which is continuously pressurizedwhen the golf car is not in use and the brake system is engaged in aparking mode. To achieve a positive seal in response to relatively highstatic hydraulic pressures present in brake system 50, eleastometerseals replace metal-to-metal contact on all sealing surfaces, includingair bleeder valves found on caliper assemblies 48.

Hydraulic brake system 50 also includes two separate damping systems toprovide a controlled release of brake pedal 82. A first damping systemis a mechanical damping system implemented by applying a damping greaseto a pivot shaft housed within a stationary sleeve. The helical springreturns brake pedal 82 to its non-operative position. The damping greasehas a viscosity which varies in accordance with the displacement speedof the pivot shaft. At slower speeds, the damping grease acts as alubricant. At higher speeds, the damping grease provides a viscousaction between two adjacent surfaces which retards the rate at which thepivot shaft may be rotated with respect to the stationery sleeve. Thus,the damping grease is applied to both the pivot shaft and the stationarysleeve. As the pivot shaft rotates with respect to the stationarysleeve, the viscous action ensures a controlled rate of upward travel ofbrake pedal 82. This viscous action also significantly reduces thenormal multiple vibration pulses that occur at the top of the brakepedal stroke in convention mechanical systems.

A second damping system utilizes a dampened hydraulic fluid flow tomaintain a controlled return of parking brake 82 pedal to itsnon-operative position. This controlled rate of upward movementminimized noise inherent in the stopping of brake pedals at the top oftravel in conventional brake systems.

Hydraulic fluid travels through a spiral grooved return path to restricthydraulic fluid flow during pedal return. The fluid damping path enablesa fluid flow return rate which encourages the brake pedal upward at areasonable rate so as to maintain contact with the foot of the operatorwhile the operator lifts upward with his or her foot. Thus, the operatorfeels the brake pedal firmly on the bottom of the operator's foot, whilethe return rate is sufficiently slow to prevent banging when the brakepedal reaches the top of travel.

Referring now to FIGS. 4-8, a preferred mode of practicing the inventionwill be described. The brake actuator and release assembly 50 includesas its major components 1) a master cylinder 60, 2) a hydraulicaccumulator 62, and 3) an integrated brake pedal and accelerator pedalassembly 58. All of these components are mounted on a common supportbracket 66 that is formed from a single metal stamping. As best seen inFIGS. 4-8, the. support bracket 66 has an open rear end, inboard andoutboard sidewalls 68 and 70, and a front wall 72 connecting thesidewalls 68 and 70 to one another. Mounting flanges 74, 76, and 78extend outwardly from the sidewalls 68 and 70 and the front wall 72 forconnection to a support such as the front wall 42 of the operator'scompartment.

The integrated brake pedal and accelerator pedal assembly 58 and thehydraulic accumulator 62 can be used either in combination orindependently of one another and are applicable to the illustrated brakesystem 50 as well as to a variety of other systems. Each of thesecomponents will be described in turn.

The integrated brake pedal and accelerator pedal assembly 58 is usablewith the hydraulic brake system 50 as well as a more traditionalmechanical cable-actuated brake system. It includes a brake pedal 80, anaccelerator pedal 82, and a locking mechanism 84. The assembly 58 canperform several distinct functions. First, the brake pedal 80 can beactuated to perform a service braking operation. Second, the lockingmechanism 84 can latch the brake pedal 80 in a locked, actuated positionto hold the service brakes 52 in their engaged position. Third, thebrake pedal 80 can operate, in conjunction with the accumulator 62, tofacilitate brake pedal latching and store energy to help assure that thebrakes 52 will remain in their locked position despite creep that mayoccur within the system. Fourth, the locking mechanism 84 can bereleased using either the brake pedal 80 or the accelerator pedal 82without actuating any secondary brake release mechanism.

The brake pedal 80 includes a pivot shaft 86, a lever arm 88 extendingdownwardly from the pivot shaft 86, and a pad 90 mounted on the bottomend of the lever arm 88. As best seen in FIGS. 6, 7, and 8, the pivotshaft 86 is mounted on a plastic sleeve 92 so as to be rotatable withrespect thereto, and the plastic sleeve 92 is, in turn, mounted on amain pivot shaft 94. Shaft 94 is rotatably supported on the supportbracket 66 and also serves as the pivot shaft for the accelerator pedal82 (discussed below). The pivot shaft 86 is lubricated via a syntheticdamping grease injected into the space between the pivot shaft 86 andthe plastic sleeve 92. The damping grease preferably that comprise onethat exhibits good lubrication characteristics at low rotationalvelocities but that actually serves to damp or inhibit shaft rotation athigher rotational velocities. The preferred grease is NYE PG-44A, whichis manufactured by NYE Lubricants, Inc. This grease is an extremelystiff consistency, inorganically gelled, water resistant, rust-inhibiteddamping grease based on a high molecular weight polymeric-base oil. Thelever arm 88 preferably is formed from steel encased in a plastic sleeve(not shown) in order to protect the steel from corrosion. The pad 90 maycomprise any suitable foot actuated pad mounted on the end of the leverarm 88. A torsion spring 96, serving as a brake pedal return spring, ismounted on the pivot shaft 86 on one side of the lever arm 88. Inaddition, a plastic block 98 is mounted on the upper surface of thelever arm 88 to form part of the lock mechanism 84 as detailed below.

Referring particularly to FIG. 5, a master cylinder actuating pinsupport arm 100 is mounted on the pivot shaft 86 adjacent the inboardside of the lever arm 88 so as to rotate with the lever arm 88. Anactuating pin 102 is mounted on the support arm 100 so as to rotate withthe pivot shaft 86. The pin 102 is coupled to a main piston 104 of themaster cylinder 60 via a roller 103 and a strap 105 so that the brakepedal 80 and master cylinder piston 104 always move together. Theactuating pin 102 comprises an eccentric pin that is mounted in anaperture 106 in the support arm 100 so as to extend laterally toward thebrake lever arm 88. A head 108 on the pin 102 can be rotated to rotatethe thicker portion of the eccentric pin 102 either towards or away fromthe master cylinder main piston 104, thereby eliminating any play ordead space between the brake pedal 80 and the master cylinder mainpiston 104 after assembly of all components.

The locking mechanism 84 is operable to automatically latch the brakepedal 80 in its locked position upon depression of the brake pedal 80 toa latch point and to automatically unlatch the brake pedal 80 from itslocked position to release the brakes 52 upon brake pedal overtravelbeyond the latch point. The locking mechanism 84 also is configured torelease the brake pedal 80 under power of the accelerator pedal 82. Thelocking mechanism 84 may comprise any structure having at least oneof 1) single point latching capability, 2) the ability to release thebrakes 52 upon brake pedal overtravel beyond its latched position, and3) a kickoff mechanism that permits accelerator pedal release of thebrake pedal 80. The illustrated locking mechanism 84 includes the block98 on the brake pedal lever arm 88, a control arm 110 pivotally mountedon the brake pedal 80, a swing arm 112 pivotally mounted on the supportbracket 66, and an over-center spring 114 that is coupled to the controlarm 110 and to the swing arm 112 so as to bias the swing arm 112downwardly during service braking and to bias the swing arm 112 upwardlyduring a latch and release cycle.

The control arm 110 comprises a metal plate pivotally mounted on theblock 98 of the brake pedal 80 via a pivot pin. Control arm 110 hasinner and outer faces and front and rear ends. The rear end presentsdetents 118 and 120, and a lug 122 is mounted on the outer face near therear end near the axis of the pivot pin. During a brake lock and releasecycle, detents 118 and 120 cooperate with a dog or pawl 124 on the swingarm 112. A cushioned stop is mounted on the inner face of the controlarm 110 in front of the pivot pin. The stop has first and second arcuatesurfaces that selectively engage corresponding first and secondcushioned posts on the block 90 during the brake pedal lock and releasecycle as detailed below. Finally, a post 136 extends outwardly from afront end portion of the outer face of the control arm 110 forconnection to a front end of the over-center spring 114.

The swing arm 112 supports the dog 124 and the cam 125. It also supportsa cam follower 138 that rides along a cam 140 on the block 98. Theentire swing arm 112 is mounted on a pivot tube 142 that extendslaterally across the support bracket 66 and that is rotatably supportedon a support pin 146. Support pin 146 is, in turn, mounted in aperturesin the opposed sidewalls 68 and 70 of the support bracket 66. A pair ofcam follower support arms 144 extend forwardly from the pivot tube 142in a spaced-apart relationship. The cam follower 138 is rotatablymounted on the front ends of the support arms 144, and a cushionedelastomeric bumper 148 is mounted on the rear ends of the support arms144. The cam follower 138 comprises a roller mounted on the support arms144 by a roll pin. The bumper 148 serves as a stop for the brake pedal80 when the brake pedal is in its at rest or fully released positionseen in FIG. 7. The dog 124 is positioned laterally outwardly of theoutboard cam follower support arm 144 and is configured to cooperatewith the detents 118 and 120 on the control arm 110. The cam 125 isformed from a common stepped lug with the dog 124 and is positioned soas to be engaged by the lug 122 on the control arm 110 during a latchingoperation. A spring support bracket 150, disposed outboard of the dog124, supports a post 152 to which the over-center spring 114 isconnected. The locations of the posts 152 and 136 on the swing arm 112and the control arm 110 are selected relative to 1) one another, 2) therotational axis of the cam follower, 3) the pivot axis of the brakepedal 80, and 4) the pivot axis of the swing arm 112 to cause the spring114 to move across the pivot axis of the swing arm 112 at selectedphases of the brake pedal depression and return processes so as toselectively assist brake pedal locking and unlocking. In the illustratedembodiment, the over-center spring is 30°-40° below the horizontal whenit is in its first over-center position and a corresponding amount abovethe horizontal when it is in the second over-center position.

The block 98 is mounted directly on the upper surface of the brake pedallever arm 88 and serves as a support structure for several othercomponents of the locking mechanism 84. It has the cam 140 formeddirectly on the upper or rear surface thereof. The cam 140 is straightalong the majority of its length but has an arcuate portion 154 at itslower end surface formed from a cutout in the block 98. Arcuate portionis dimensioned such that the cam follower 138 will rest in the arcuateportion 154 in a locked position of the brake pedal 80.

A generally L-shaped toggle arm 156 is pivotally mounted on the innerlateral surface of the block 98 adjacent the swing arm 112. The togglearm 156 includes 1) a first leg 158 and 2) a second leg 160 that extendsgenerally orthogonally from the first leg 158. The first leg 158 isbiased into contact with a post 162 on the block 98 by a return spring164. The second leg 160 cooperates selectively with a lug 166 on theswing arm 112 so as to prevent swing arm pivoting motion during theinitial phase of brake pedal depression and to subsequently permit theswing arm 112 to fall into its locking position when the lug 166 clearsthe second leg 160, thus allowing only one contact sound to be heard.

Finally, a kickoff arm 170 is mounted on the inboard end of the pivottube 142 at a location beyond the inboard cam follower support arm 144.The kickoff arm 170 extends forwardly and outwardly from the pivot tube142 so as to extend beyond the inboard sidewall 70 of the supportbracket 66 and so as to be engaged by the accelerator pedal 82 uponinitial accelerator pedal depression.

The accelerator pedal 82 is mounted on the inner distal end of the pivotshaft 94 at a location outside of the inboard sidewall 70 of the supportbracket 66. It includes 1) a lever arm 172 that extends downwardly fromthe pivot shaft 94 and 2) a pad 174 that is mounted on the distal end ofthe lever arm 172. A portion of the lever arm 172 is positioned closelyadjacent the kickoff arm 170 so as to engage the kickoff arm 170 uponinitial accelerator pedal depression. In addition, a non-contactaccelerator pedal position sensor 178 is positioned inside the lever arm172 in order to provide an indication of accelerator pedal actuation.The accelerator pedal 82 is biased to its deactuated position by areturn spring 180.

In operation, the integrated brake pedal and accelerator pedal assembly54 assumes the position illustrated in FIGS. 5-6 when the brakes 52 arenot engaged. At this time, the brake pedal 80 assumes an at rest orfully released position in which it is pivoted to its rearward-mostextent in which the front face on the block 98 engages the bumper 148 onthe swing arm 112. The cam roller 138 on the swing arm 112 is located atits maximum possible distance from the arcuate portion 154 of the cam140. In addition, the over-center spring 114 is in its first over-centerposition in which it biases the control arm 110 to the position in whichits centerline is beneath the pivot axis of the swing arm 112. Ittherefore biases the swing arm 112 downwardly.

Next, the operator engages the brakes 52 by pressing downwardly on thepad 90 to swing the brake pedal 80 clockwise into a service brakingposition. This pivoting motion causes the master cylinder actuating pin102 to drive the roller 103 and master cylinder main piston 104forwardly to effect service braking. After the service braking strokeends, but before the brake pedal 80 reaches it latch point, the lug 166on the swing arm 112 rides along the second leg 160 of the toggle arm156 to hold the cam roller 138 away from the cam face 140 and to holdthe dog 124 and cam 125 on the swing arm 112 away from the control arm.As a result, service braking and subsequent brake pedal depressiontoward the latch point occur without contact between the latchingcomponents of the locking mechanism 84, thereby avoiding the generationof contact sounds that otherwise could give a false audible indicationof pedal locking. The over-center spring 114 remains in its firstover-center position at this time. The control arm 110 therefore remainsin the position in which it cannot latch against the swing arm 112. As aresult, the brake pedal 80 will return to its released position if theoperator removes his foot from the pad 90 without additional brake pedaldepression.

At the end of service braking stroke and well beyond it, the lug 166 onthe swing arm 112 clears the second leg 160 of the toggle arm 156 sothat the swing arm 112 drops through an arc to a position in which thecam 125 engages the lug 122 on the control arm 110. This delayeddropping of the swing arm 112 has several benefits. For instance, asdescribed above, it permits the dog 124 and cam 125 on the swing arm 112to clear the detents 118 and 120 and the dog 122 on the control arm 110so as to prevent a false audible indication of brake pedal locking.Moreover, it prevents the swing arm 112 from swinging towards its lockedposition until the over-center spring 114 is stretched sufficiently tostore enough potential energy to effectively assist in swing armmovement into its locked position. In addition, the solid contactbetween the cam 125 and the lug 122 that occurs when the swing arm 112drops into place produces a distinctive “clicking” sound that providesan audible indication to the operator that the brake pedal 80 has movedinto a position in which it can be locked.

When the operator releases his foot from the brake pedal 80 afterdepressing it to its locked position, the brake pedal returns a verysmall amount to permit the over-center spring 114 to move from its firstover-center position to the second over-center position as a result ofthe swing arm cam 125 pushing the control arm dog 122. As a result ofthis movement, the control arm 110 pivots rapidly from this position tothe latched position. Because the dog 122 is located very close to thepivot axis of the control arm 110, a very small range of axial brakepedal movement (on the order of a few thousands of an inch) results in60° or more of control arm pivoting movement. This relationship reducesthe work required of the over-center spring 114 during the latchingprocess. The second face 130 on the stop 126 now engages the second post134 on the block 98, and the first or lower detent 118 on the controlarm 110 now engages the dog 124 on the swing arm 112 to lock the swingarm 112 in position. This motion provides a distinctive clicking soundthat provides an audible indication to the operator that the brake pedal80 has been locked. The brake pedal 80 will thereafter remain in thelocked position under the latching force of the control arm 110 when theoperator releases the brake pedal 80. However, because the spring 114 isnow in is second over-center position in which its centerline is abovethe pivot axis of the control arm 112, it biases the control arm 112upwardly rather than downwardly, thereby priming the control arm 112 forsubsequent release.

The holding force applied on the control arm 110 by the over-centerspring 114 at this time should be large enough so as not to be overcomeby any force that might inadvertently be placed upon or generatedthrough the accelerator pedal 82 by virtue of the vehicle 30 beingjostled during shipment or by rough treatment by errant operators.However, this holding force need not be very large because any momentarm which might tend to cause the swing arm 112 to swing out of itslocked position is very small. As a result, a relatively weak spring(having a spring load on the order of 8-12 lb can be used as theover-center spring 114.

The brakes 52 may be released by operating either the brake pedal 80 orthe accelerator pedal 82 to unlatch the brake pedal 80 from its lockedposition. To release the brakes using the brake pedal 80, all theoperator need do is depress the pedal 80 beyond its locked position toan overtravel position. This brake pedal movement and consequent swingarm movement will cause the dog 124 on the swing arm 112 to slip out ofthe first detent 118 on the control arm 110, permitting the over-centerspring 114 to pull the swing arm 112 upwardly so that dog 124 snapsagainst the second detent 120 as seen in FIG. 10. The snapping action ofthe dog 124 against the detent 120 produces a distinctive click thatapprises the operator that the brake pedal 80 is unlatched. As a result,the brake pedal 80 will return to its at-rest position under the biasingforces of the return spring 96 and the accumulator spring 246 when theoperator releases the brake pedal 80.

The brake pedal 80 places a substantial moment on the swing arm 112during the return stroke of the brake pedal 80. The dog 124 on the swingarm 112 produces a corresponding moment on the upper surface of thedetent 120 of sufficient magnitude to pivot the control arm 110counter-clockwise. The over-center spring 114 therefore moves back toits first over-center position so that it again biases the swing arm 112downwardly. In addition, the lug 166 on the inner lateral surface of theswing arm 112 engages the second leg 160 of the toggle arm 156 duringthe return stroke to cause the toggle arm 156 to pivot clockwise topermit unobstructed movement of the lug 166 past the toggle arm 156. Thetoggle arm 156 then drops back into its initial position under thebiasing force of the spring 164 so that it is primed for the nextservice braking cycle.

Brake pedal release using the accelerator pedal 82 occurs in similarsequence. The operator presses downwardly on the accelerator pedal 82 sothat the lever arm 172 engages the kickoff arm 170. This engagementforces the swing arm 112 to swing clockwise about the pivot tube 142 todrive the control arm 110 to pivot as described above. As before, thismovement unlatches the swing arm 112 from the control arm 110 andpermits the brake pedal 80 to return to its at-rest position under thebiasing force of the brake pedal return spring 96 and the accumulatorspring 246. Also as before, this movement forces the control arm 110 andover-center spring 114 back to the initial position. Because the cutout154 in the cam surface 140 is tangential to the swing arm pivot arc, thecam roller 138 simply moves circumferentially along the cam surface 140during the initial, accelerator pedal imposed phase of the unlatchingoperation without resistance from the rather substantial return forceimposed on the brake pedal 80 by the brake pedal return spring 96 andthe accumulator spring 246. Brake pedal unlatching therefore impartslittle resistance to accelerator pedal motion, and brakes 52 aredisengaged after the first 1-3 inches of accelerator pedal stroke withminimal operator effort. As a result, the operator can “feather”accelerator pedal motion so that the brakes 52 can be disengaged withoutover-depressing the accelerator pedal 82. This eliminates jerky motionor quick starts often associated with golf carts and other light-dutyvehicles.

The master cylinder 60 and hydraulic accumulator 62 are configured totranslate the mechanical actuating forces generated by brake pedaldepression into hydraulic pressure that first engages the brakes 52 andthat then stores additional energy for holding the brakes 52 in theirengaged condition. This energy storage provides several benefits. Forinstance, it permits the brake system 50 to make up for “creep” or fluidpressure loss that may occur due, e.g., relaxation of elastomericcomponents of the system. Moreover, it can assist in returning the brakepedal 80 to its at rest position following release of a locked brakepedal.

Referring to FIGS. 4, 5, 7, and 8, the master cylinder 60 is generallyconventional. It includes a housing 200 having an internal horizontalbore 202 formed therein. A reservoir 204 is formed above the bore 202for storing hydraulic fluid. The bore 202 has an upper fill inlet 206and a rear outlet 208. The inlet 206 cooperates with the reservoir 204.The rear outlet 208 opens into an accumulator chamber 210, detailedbelow. The master cylinder main piston 104 is slidably mounted in thebore 202 so as to extend rearwardly from the rear end of the bore 202and into contact with the roller 103. As a result of thisarrangement, 1) depression of the brake 80 and consequent swingingmovement of the actuator pin 102 and roller 103 drives the main piston104 forwardly through the bore 206 to pressurize the outlet 208, and 2)release of the brake pedal 80 permits the main piston 104 to moverearwardly through the bore 202 to depressurize the outlet 208.

Referring to FIG. 7, accumulator chamber 210, as well as the remainderof the accumulator 62, may be located at any pressurized point in thebraking system 50. In the illustrated embodiment, however, the chamber210 is formed in an extension 212 of the master cylinder housing 200extending essentially colinearly with the bore 202 so as to reduce thenumber of parts in the accumulator 62 and to facilitate assembly. Theaccumulator chamber 210 has a first orifice 218 in a rear wall thereofthat opens directly into the master cylinder outlet 208, and a secondorifice 220 in an upper wall thereof that communicates with a bleederport 222 and a brake supply orifice 224 in the master cylinder housingextension 212. The orifice 224 is connected to the front and/or rearvehicle brakes 52 via associated brake lines 46 of FIG. 2.

An accumulator drive piston 214 and a one-way restrictor valve 216 aremounted in the accumulator chamber 210. The accumulator drive piston 214is slidably mounted in the chamber 210 so as to extend beyond a rear endof the master cylinder extension 212 and into contact with theaccumulator spring assembly 58. The one-way restrictor valve ispositioned forwardly of the accumulator drive piston 214 and is biasedtoward the front of the chamber 210 by a return spring that is seated onthe one-way restrictor valve 216 at its front end and on the accumulatordrive piston 214 at its rear end.

The purpose of the one-way restrictor valve 216 is to damp return fluidflow into the master cylinder 60 from the accumulator chamber 210 uponrelease of the brakes 52, thereby inhibiting the pronounced brake pedalsnapback effect exhibited by most park and hold brake systems of thistype. The energy stored in the accumulator 62 and the brakes 52 insteadis released more gradually, permitting a much smoother brake pedalreturn.

The hydraulic accumulator 62 performs several beneficial functions. Forinstance, it reduces the effort required by the operator to depress thebrake pedal 80 to its locked position. It also stores energy generatedupon manual pressurization of the hydraulic fluid in a form that canthen be used to maintain the brakes 32 in their engaged positions afterthe brake pedal 80 is locked. Finally, it assists in returning the brakepedal 80 to its released position upon brake pedal unlocking. Thepreferred accumulator structure is one that has a minimum number ofcomponents and that can be readily assembled as a unit offsite and thenattached to the remainder of the brake assembly 50 by an unskilledoperator. Towards these ends, the hydraulic accumulator 62 is a springtype accumulator taking the form best seen in FIG. 7. It includes aretainer 240, a movable compression plate 242 disposed at the rear endof the retainer 240, a cap 244 affixed to the front end of the retainer240, and a compression spring 246 captured between the compression plate242 and the cap 244.

The retainer 240 includes a front mounting plate 248 and a plurality(preferably two) straps 250 that extend rearwardly from the mountingplate 248. The mounting plate 248 has an internally threaded post 252and a pair of tangs 254 located radially outside of the post 254 andbent in opposite directions. The threaded center post 252 screws ontoexternal threads 256 on the master cylinder housing extension 212, andthe tangs 254 lock into slots 258 in the front wall 72 of the supportbracket 66 when the post 252 is fully tightened onto the master cylinderhousing extension 212. The accumulator 62 can subsequently be unscrewedfrom the master cylinder housing extension 212 only by overtorquing theaccumulator 62 in a counter-clockwise direction to release the tangs 254from the slots 258. The straps 250 serve as mounts for the cap 244 andare configured to guide and support both the spring 246 and thecompression plate 242. Each strap 250 extends rearwardly from themounting plate 248 and terminates in a hook 260 at its distal end. Thebodies of the straps 250 serve as supports and guides for thecompression plate 242 and the spring 246. The hooks 260 latch onto thecap 244 as detailed below to fix the cap in place.

The compression plate 242 includes a rear annular spring support portion262 and a cup portion 264. The cup portion 264 extends axially forwardlyfrom the center of the rear spring support portion 262 to a front nutportion 266. Spring support portion 262 presents a seat for the rear endof the accumulator spring 246. Cup portion 264 is configured to surroundthe end of the master cylinder housing extension 212 and to abut thefront end of the accumulator drive piston 214. Apertures 268 are formedin the spring support portion 262 for passage of the straps 250. Uponassembly, this relationship between the straps 250 of the retainer 240and the apertures 268 in the compression plate 242 permits thecompression plate 242 to move axially relative to the retainer 240 butprevents relative rotational movement between the compression plate 242and the retainer 240.

The cap 244 comprises a metal annular ring having a circular axiallyfront end portion 270 and inner and outer circular flanges 272 and 274.The flanges 272 and 274 extend rearwardly from the front end portion 270so as to form a groove serving as a second seat for the spring 246. Apair of hook receiving apertures are formed in the front end portion 270adjacent to corresponding notches 278. The notches 278 are configured toreceive the straps 250 and the hooks 260 of the retainer 240, therebylocking the cap 244 onto the retainer 240.

The spring 246 is precompressed a substantial amount as a result of apreassembly process. As discussed in more detail below, this springprecompression sets a threshold pressure below which substantially allwork performed by the master cylinder 60 is applied toward fluidpressurization and above which the majority of the work performed by themaster cylinder 60 is applied toward energy storage in the accumulator62. The amount of precompression required for a particularpressurization threshold level will vary depending on the spring rate ofthe spring 246 and its caged height. The spring 246 of the illustratedembodiment has a free length of about 9″ and a spring rate of 25 lbs/in.It is precompressed to an installed length of approximately 4″ duringthe assembly process to provide a threshold pressure of about 800-850psi.

The precompression of the accumulator spring 246 is selected to set thethreshold pressure to a level well above the lockup point of the brakes52 but well below the single latch point of the brake pedal 80. In asystem in which the brake pedal is latched in position 8″ into itsstroke, service braking is performed in the first 2 to 3″ of brake pedalstroke even under panic stop conditions. In fact, brake lockup typicallyoccurs after no more than 2-½″ of brake pedal stroke. Typical lockuppoints for fully burnished and unburnished brakes are denoted as such inFIG. 8.

Additional brake pedal depression past the threshold point 286compresses the accumulator spring 246, thereby storing the energy ofmaster cylinder actuation in the form of potential energy in the spring246. System pressure rises at a much slower rate during this phase ofpedal actuation, as represented by the shallow portion 288 of the curve282. This effect results from the fact that the incremental increase ininput force required to compress the spring 246 is substantially lowerthan the incremental increase in input force required to additionallypressurize the hydraulic fluid. As a result, resistance to brake pedalmovement during this second phase of brake pedal actuation increases ata much slower rate than during the first phase.

In the illustrated embodiment, the transition point 286 between thefirst and second phases of brake pedal actuation occurs at approximately800-850 psi of hydraulic pressure. Pressure thereafter rises graduallyto about 900-950 psi when the brake pedal 80 is latched in its lockedposition and the end of the second phase of its actuation stroke. Thecompression spring 246 is compressed about ½″ at this time. At least50%, and possibly at least 65% or more, of the total pedal strokerequired to latch the brake pedal 80 in its locked position is consumedin the second phase of brake pedal actuation. As a result, by the end ofthis phase, more than ample energy is stored in the accumulator 62 tohold the brakes 52 and to return the brake pedal 80 with littleadditional effort by the operator. (The amount of energy stored by theaccumulator 62 is represented by the hatched area 292 under the curve282 in FIG. 9.)

Considerable work is performed over the rather lengthy second phase ofthe brake pedal actuation stroke, but at much lower input forces thanwould be required to perform the same amount of work (and hence to storethe same amount of energy) over a shorter stroke. In fact, thetransition point 286 is reached at an operator input force of about 35lbs, and only an additional 25 lbs of input force is required to depressthe brake pedal 80 to its latch point. This is in contrast to thedrastically higher input force that would be required to pressurize thefluid to a much higher level if the operator were to press the brakepedal 80 to its latch point without an accumulator in the system (seethe phantom line 290 in FIG. 9). Hence, the accumulator 62 greatlyfacilitates brake pedal latching and reduces the precision required toachieve the latch point because the operator strokes the pedal a greatdistance easily.

Upon brake pedal release, the one-way restrictor VALVE 216 immediatelyseats against the front end of the chamber 210 under the force of thereturn spring 230, thereby preventing rapid depressurization of theaccumulator chamber 210. The damping effect provided by this restrictedfluid flow imposes a relatively low return speed on the brake pedal 80that continues for a period of time. The brake pedal 80 consequentlyreturns to its initial position without any undesirable rapid snapbackthat otherwise would produce substantial wear and tear on the system andeven risk injury to the operator. The damping grease between the brakepedal pivot shaft 86 and the stationary sleeve 92 additionally dampsbrake pedal return movement at this time. However, the combined dampingeffect provided by the one-way restrictor valve 216 and the dampinggrease does not overly-damp brake pedal return. Instead, the brake pedal80 is biased by the springs 96 and 246 to quickly follow the operator'sfoot without pushing the foot upwardly too fast. The remaining, smallsnapback impact forces resulting from this moderate return speed areabsorbed by the elastomeric bumper 148 on the swing arm 112 when thebrake pedal 80 reaches its at-rest or fully released position, resultingin a virtually noiseless and vibration less pedal return.

FIG. 10 depicts a hydraulic brake system 310 arranged similarly tohydraulic brake system 50 of FIGS. 1-3. Hydraulic brake system 310utilizes a drum brake system rather than a disk brake system to applybraking force at the wheels. Components of hydraulic system 310 whichare similar to the components described with respect to FIGS. 1-3 willbe referred to using identical reference numerals.

Of particular interest in FIG. 10, brake system 310 is embodied as adrum brake system which includes a brake cylinder and shoe assembly 312which operates in response to hydraulic fluid pressure applied throughhydraulic control line 46. Brake cylinder and shoe assembly 312 includesa brake cylinder which presses brake shoes radially outward againstbrake drum 314. Brake drum 314 on its outboard side connects to wheels14. Application of hydraulic fluid pressure through hydraulic controllines 46 causes brake cylinder and shoe assembly 312 to press againstbrake drum 314, thereby generating a frictional force retarding movementof wheels 14. Accordingly, hydraulic brake system 310 operates asdescribed above, except that application of braking pressure occursthrough a drum brake system rather than through a disk brake system.

In yet another embodiment of the present invention, FIG. 11 depicts ahydraulic brake system 320 which utilized a band brake system to retardmovement of drive shafts 34. FIG. 11 is generally arranged as describedabove with respect to FIGS. 1-3 and 10 except that the brake mechanismwill be described with respect to a band brake system, rather than adisk or drum brake system. Accordingly, like reference numerals fromthese figures will be used to described similar components in FIG. 11.

Hydraulic brake system 320 utilizes displacement of brake pedal 80 andlinkage 42 to generate a hydraulic fluid pressure from master cylinder60 into hydraulic control lines 46. Hydraulic control lines 46 operate aband brake assembly 322. Band brake assembly 322 includes a brakecylinder 324 rigidly connected to drive shaft 34. Brake cylinder 324 isencircled by brake band 326. In response to hydraulic to fluid pressure,brake band 326 circumferentially restricts around brake cylinder 324 togenerate a frictional force. A frictional force retards movement ofdrive shafts 34 and correspondingly retards movement of wheels 14 tothereby crate a braking force. When hydraulic fluid pressure inhydraulic control line 46 is reduced, brake band 326 reduces thecircumferential constriction thereby reducing the braking force.

FIGS. 12-17 show a preferred embodiment of caliper assembly 48 and itsinterconnection to golf car 10. FIG. 12 shows a left brake assembly 500Lwhich is composed of the integral hub and rotor assembly 502 which has arotor portion 504 and a wheel hub portion 505. Brake assembly 500Lfurther has a caliper assembly 506 which is attached by two throughbolts 508 to affixed flange 510 rigidly mounted to the rear axle housing511.

Caliper assembly 506 has a caliper outboard half subassembly 512 and acaliper inboard half subassembly 514. Caliper inboard half 514 has aninput fluid port 516 for receiving fluid from the hydraulic brake line521 and a fluid output port 517 for providing fluid to the right brakesystem 50OR (see FIG. 13). Caliper inboard half subassembly 514 has ableeder valve 518 for bleeding air from the brake lines 521 duringrepair or installation.

FIG. 13 shows a right brake assembly 500R, which is composed of the samecomponents as those shown in the left brake assembly 500L of FIG. 12, inmirror image. form. Caliper assembly 506 holds a pair of brake pads 518and 519 adjacent to rotor 504 of the integrated hub and rotor assembly502. Pads 518 and 519 move in response to hydraulic force generated byfluid under pressure applied to input port 516R. The integrated hub androtor assembly 502 is held onto drive shaft 536 by a hex castle nut 538and cotter pin 540.

FIG. 14 shows an exploded view of caliper assembly 506, which revealsthat the caliper inboard half subassembly 514 and caliper outboard halfsubassembly 512 each have a pair of piston actuators 520. Each actuatorhas a conventional polymeric outside seal 522, which elastically deformswhen the pistons are moved forwardly to press against the brake pads 518and 519, and which undeform to pull the piston away from the rotorportion 504 when the fluid pressure is removed. Between the halves ofthe caliper 506 is a pair of conventional elastomeric O-rings 525 whichfunction to help prevent leakage of hydraulic fluid moving throughinternal passages within each half sub assembly 512 and 514 and betweenthe halves of the caliper 506. Disposed immediately adjacent the O-rings225 is a pair of through holes 528 for accepting through mounting bolts530 (not shown) (in FIG. 14). Also shown is through bolt 532 whichfunctions to secure brake pads 519 and 518 in their proper alignmentwith the rotor portion 504. Wire spring clips 542 and 544 generally arefurther provided to hold the brake pads in place.

FIG. 15 is a perspective view of caliper assembly 506 of the currentinvention. Shown are the through bolts 530 which function to hold thecaliper inboard half subassembly 514 and caliper outboard halfsubassembly 516 together. Also shown are through bolts 532 holding thebrake pads 518 and 519 in proper position between the piston actuators520.

FIG. 16 shows a bottom view of the caliper brake assembly 500. Shown isthe relationship of the pads 518 and 519 with the actuating pistons 520.As can be seen, the pads 518 and 519 define a space wherein the rotorportion 504 is located.

FIG. 17 is a diagram of the integral wheel hub and rotor assembly withcaliper disposed within the small diameter of the golf cart wheel 542.As can be seen, the low profile caliper 506 can fit within the smalldiameter of the golf cart wheel. The lower profile of the caliper 506allows for incorporation of a disk brake system onto a golf cart.

Further details of the brake caliper assembly 506 will now be described.Subassembly 512 includes a metal caliper housing preferably preparedfrom an iron or aluminum alloy casting, and subassembly 514 includes asimilarly made metal caliper housing. Each of these caliper housings maybe precision-machined to conventional tolerances to have their flatexterior mating surfaces, the through holes, and substantiallycylindrical pockets for receiving the brake pistons, that are shown inthe FIGS. 12 through 15, formed to proper size. Using conventionaltechniques, internal passages for hydraulic fluid are formed withincaliper housings to provide hydraulic fluid from the inlet port to thebackside of the respective brake piston pockets. Flat machined surfaceson the end portions of one caliper housing of subassembly 512 match upwith and bear tightly against corresponding flat machined surfaces onthe caliper housing of subassembly 514 when the two mounting bolts 530are drawn tightly against the rigid mounting flange 510 to which theoverall assembly 506 is rigidly mounted. The side face of mountingflange 510 contacting the adjacent caliper housing of assembly 512 isparallel to the rotor 504. The through holes in the caliper housings forthe mounting bolts 530 are perpendicular to these machined surfaces,thus ensuring that faces of the brake caliper pistons are sufficientlyparallel to the parallel opposed faces of rotor 504 to ensuresubstantially uniform wear on brake pads 518 and 519.

Each through bolt is substantially centrally positioned relative toopposed flat machined surfaces of the end portions of the caliperhousings of caliper subassemblies 512 and 514. In this manner,tightening bolts 530 ensures slight compression of O-rings 525, toeliminate the possibility of any hydraulic leak between the adjacenthousings. Since only two bolts are required to mount caliper theassembly 512 to flange 510, minimal effort is required for finalassembly to the vehicle axle. This means that brake caliper assembly 512can be fully assembled in a location remote from the final assemblyplant for the small utility vehicle, function-tested, and then shippedwhile filled with hydraulic fluid if desired.

Caliper assembly 506 has a low compact profile when viewed in sideelevation. As best shown in FIG. 17, the clearance between the radiallyoutermost points of caliper housings of subassemblies 512 and 514, andthe inner generally cylindrical rim surface of the wheel are preferablyin the range of about 3 mm (about 0.1 inch) to about 20 mm (about{fraction (8/10)} inch), with a range of about 5 mm (about {fraction(2/1.0)} inch) to about 12 mm (about 2 inch) being presently preferred.Such tight clearances are made possible in part by using sufficientlythick and stiff caliper housings which are further rigidified andstabilized by the use of two quality mounting bolts 530 and asufficiently stiff mounting flange to avoid any significant lateral orradial flexing or distortion of the caliper assembly during intensebraking, up to and including full rotor/wheel lock-up. In this regard,the outer end portions of caliper housings through which the throughbolts 530 are run, are as shown generally thicker (that is, in thedirection of the axis of the rear axle of the vehicle) than they arehigh (that is, a the radially outward direction from the axis of therear axle of the vehicle).

The use of two sets of opposing pistons in the opposed half calipersubassemblies 512 and 514 also provides additional benefits. First, theopposed piston arrangement provides balanced opposing forces on oppositesides of the rotor, thus allowing high hydraulic braking forces to beapplied. Secondly, the two piston actuators 520 in subassembly 512 areslightly angularly spaced apart from one another. By using twospaced-apart brake pistons on each caliper subassembly, a generallyoblong, kidney-shaped relatively thick brake pad may be used as shown,thus maximizing the amount of surface area of the brake pad. Its largesize helps minimize the rate of brake pad surface wear during repetitivebraking over a period of months and years. The oblong brake pads arepreferably made in any conventional or suitable manner, with reinforcinga back plate portion as shown, to help ensure minimal deflection andgood contact between the rotor surface and brake pad surface, even inthe central region of the brake pad between the two brake pistons. Armedwith the teachings and illustrations within the present disclosure, thedesign and construction of compact, low-profile dual piston brakecaliper assembly of the present invention with its long-life brake padsneed not be further described, since the design and construction oflarger, less space-efficient conventional two-piston and four-pistonbrake caliper assemblies are well understood, and details from thosedesign and construction techniques, where space and compact is not anissue, can be readily adapted into the present environment.

While the invention has been described in its presently preferred form,it is to be understood that there are numerous applications andimplementations for the present invention. Accordingly, the invention iscapable of modification and changes without departing from the spirit ofthe invention as set forth in the appended claims.

What is claimed is:
 1. A brake actuator assembly for a park and holdhydraulic brake system of a vehicle comprising: (A) a brake pedal, for ahydraulic braking system, which is pivotal, under the imposition ofmanual operating forces, from an at-rest position 1) through anoperating stroke in which the vehicle's brakes are engaged and in whichsaid brake pedal returns automatically to said at-rest position uponrelease of the manual operating forces to release the brakes, 2) througha locked position which is located beyond an end of said operatingstroke, and 3) to a beyond-lock position which is located beyond saidlocked position; (B) a brake pedal locking mechanism which cooperateswith said brake pedal so as to 1) automatically latch said brake pedalin said locked position upon movement of said brake pedal into saidlocked position, thereby holding the brakes in their engaged conditionupon release of the actuating forces, and 2) automatically unlatch saidbrake pedal from said locked position upon movement of said brake pedalinto said beyond-lock position, thereby permitting return of said brakepedal to said at-rest position upon release of the actuating forces andreleasing the brakes; (C) an accelerator pedal; and (D) a kickoffmechanism which couples said accelerator pedal to said brake pedallocking mechanism and which actuates said brake pedal locking mechanismto unlatch said brake pedal from said locked position upon actuation ofsaid accelerator pedal.
 2. An actuator assembly as recited in claim 1,wherein said locking mechanism has a single latch point which providesfor a single locked position of said brake pedal and a single audibleindication to an operator that said brake pedal has been depressedsufficiently to be latched in its locked position.
 3. A method ofenergizing a hydraulically actuated service brake of a vehicle andholding said brake in its engaged condition, comprising: (A) driving abrake pedal through an actuation stroke to manually actuate a mastercylinder to generate hydraulic pressure, wherein, during a first phaseof said actuation stroke, at least substantially all work performed bysaid master cylinder is applied toward hydraulic pressureintensification, and wherein, during a second phase of said actuationstroke, at least a portion of the work performed by said master cylinderis applied towards energy storage in a hydraulic accumulator; and (B)latching said brake pedal in a locked position in said second phase ofsaid actuation stroke to hold said service brake in its engagedcondition with the assistance of stored energy from said accumulator,said step of latching including making a single audible sound toindicate that the brake pedal is in said locked position.
 4. A method tocontrol hydraulic brake actuation of a vehicle comprising: (A) manuallydriving a brake pedal to pivot from an at-rest position and into anoperating position; then (B) manually driving said brake pedal throughsaid operating position and to a locked position in which a lockingmechanism latches said brake pedal in said locked position, whereby saidlocking mechanism provides a single audible indication to an operatorthat said brake pedal had been depressed sufficiently to be latched insaid locked position; (C) unlatching said brake pedal from said lockedposition by selectively and alternatively 1) manually driving said brakepedal to an over-travel position which is located beyond said lockedposition and in which said locking mechanism automatically unlatchessaid brake pedal, and 2) manually driving an accelerator pedal intoengagement with a kick-off mechanism to automatically manipulate saidlocking mechanism to unlatch said brake pedal; and then (D) permittingsaid brake pedal to return to said at-rest position.